Effects of Training on Muscle Performance Dr Taha Sadig Ahmed . Physiology Department , College of Medicicine , King Saud University , Riyadh
Objectives • At the end of this lectures the student should be able to : • 1. Appreciate the effects of physical training on body health in general , and musculoskeletal system in particular . • 2. Define strength training . • 3. Identify the two types of hypertrophy . • 4. know the factors affecting hypertrophy . • 5. Understand that training induces protein synthesis in muscle . • 6. Explain the diffrernce between aerobic and anaerobic training .
Aerobic versus Anerobic Exercise • Aerobic exercise is that performed • (1) at a moderate level of intensity & • (2) over a relatively long period of time. • For example, running a long distance at a moderate pace is an aerobic exercise ( but sprinting is not) , bicycling . • Anaerobic exercise • is exercise intense enough to trigger anerobic metabolism • It is used by athletes to promote strength, speed and power and by body builders to build muscle mass. • Muscles develops differently from the case of aerobic exercise • Leading to greater performance in short duration, high intensity activities, which last from mere seconds up to about 2 minutes. • Any activity after about two minutes will have a large aerobic metabolic component.
Benefits of Exercise Training • When properly performed, strength training can provide significant functional benefits and improvement in overall health and well-being, including • Improves motor skills. • Increased bone density & prevention of osteoporosis . • Improved joint function . • Increased strength of muscles, tendons and ligaments . • These help to improve posture, provide better support for joints & thereby to reduce the risk of falls & injury during everyday life activities. • Therefore the potential for injury is reduced .
Regular exercise increases metabolism and promotes fat loss . • Elevates HDL (good , beneficial ) cholesterol. • Improves respiratory function . • Improves cardiovascular function , & prevents or delays development of atheroscleosis . • Prevents or delays development of diabetes . • By increasing the levels of dopamine, serotonin and norepinephrine, intense exercise is believed to help improve mood and counter feelings of depression . • For all the above reasons , properly performed physical exercise is considered beneficial because it produces improvement for overall health and well-being .
Q : What is Strength Training ? • Strength training :is the use of resistance to muscular contraction to build the strength , anerobic endurance and size of muscle . • There are many different methods of strength training, the most common being the use of gravity or elastic hydraulic forces to oppose muscle contraction .
Muscle Hypertrophy • Muscle hypertrophyis the increase of the size of musclecells. • It differs from muscle hyperplasia, which is the formation of new muscle cells. • Types of Hypertrophy : There are two different types of muscular hypertrophy: • 1-sarcoplasmic Hypertrophy : the volume of sarcoplasmic fluid in the muscle cell increases with no accompanying increase in muscular strength. • Sarcoplasmichypertrophy is characteristic of the muscles of body builders. • 2-myofibrillar Hypertrophy :actinandmyosincon increase in number and add to muscular strength, as well as a small increase in the size of the muscle. • Myofibrillarhypertrophy is characteristic of of the muscles weight lifters
Muscle Hypertrophy & Protein Synthesis • Progressive overloadis considered the most important principle behind hypertrophy, so increasing the weight, repetitions , and sets will all have a positive impact on growth • The first measurable effect is an increase in the neural drive stimulating muscle contraction. • As the muscle continues to receive increased demands, the protein synthetic machinery is upregulated. • This upregulation appears to begin with the second messenger system (including phospholipases, protein kinaseC, tyrosine kinase, and others).
Repeated exercise increases the number of contractile proteins ( actin & myosin filaments ) within each muscle fiber. • When number of contractile proteins increases sufficiently, myofibrils split within each muscle fiber to form new myofibrils inrease in the number of additional myofibrils hypertrophy. • Because skeletal muscle cells are unique in being multinucleate , the number of nuclei can also increase.
Factors Affecting Hypertrophy • (1) Age : During puberty , in males particularly ,hypertrophy occurs at an increased rate. • Natural hypertrophy normally stops at full growth in the late teens. (2) Exercise : • strength training , short duration, high intensity anaerobic exercises considerablyincreases hypertrophy ., • Lower intensity , longer duration aerobic exercise generally does not result in very effective hypertrophy . (3) Dietary protein : An adequate supply of amino acids is essential to produce muscle hypertrophy.
(4) Cortisol decreases amino acid uptake by muscle tissue, and inhibits protein synthesis prevents hypertrophy . . (5) Testosteroneis one of the body's major growth hormones promotes anabolism consequently promotes hypertrophy . • That is why exercising males can grow bigger muscles more easily and much faster than exercising women • Therefore , in during sport competition events , testosterone is prohibited , because it is considered a performance-enhancing anabolic drug that interfers with fair & just competition .
Aerobic & Anerobic Training • Each muscle is composed of combination of 2 types of muscle fibers but one is usually dominant • (1) Fast-Twitch (white) and (2) Slow-Twitch( red, oxidative ) fibers . • Fast-twitch (white , mostly glycolytic ) fibers • Have lower capillarity& few mitochondria because oxidative metabolism is of secondary importance • Are deficient in myoglobin & capable of anerobic metabolism • Are larger in size for strong & powerful contraction , • Have extensive sarcoplasmicreticulum for rapid release of calcium • Have many glycolytic enzymes for rapid release of energy • Anaerobic fibers uses its fuel faster than the blood and intracellular restorative cycles can resupply it & the muscle fail ( fatigues ) fast& more easily than slow-twitch .
(2) Aerobic , Slow-twich ( red ) fibers • are rich in capillaries and myoglobin , which binds oxygen , and gives the muscle as a whole its red color . These fibers rely on aerobic metabolism . • Have higher capillarity & largenumber of mitochondria to support high level of oxidative metabolism . • Have smaller fibers & innervated with small nerve fibers • Fibers are adapted for prolonged muscle activity and do not fatigue quickly .
When the goal of the exercising person is lifting heavier weights anaerobic strength training will produces hypertrophy + increased muscle • When the goal of the exercising person is not merely lifting heavier weights , but another goal such as body shaping aerobic exercise , and lower weights can be used , if desired . • At higher loads, the muscle will recruit all muscle fibres possible, both anaerobic ("fast-twitch") and aerobic ("slow-twitch"), in order to generate the most force. • However, at maximum load, the anaerobic fibers contract so forcefully that the aerobic fibers are completely shut out, and all work is done by the anaerobic processes. • In the aerobic regime, the blood and intracellular processes can maintain a supply of fuel and oxygen, and continual repetition of the motion will not cause the muscle to fail ( fatigue ) easily
Nutrition & Training • Muscular training must be matched by good diet • Adequate proteinis for building skeletal muscle . • High-protein diet does not impair kidney function , unless the person has pre-existing kidney diseases . • An adequate supply of carbohydrates (5-7g per kg) is also needed as a source of energy and for the body to restore glycogenlevels in muscles. • Wateris consumed throughout the course of the workout to prevent poor performance due to dehydration .